This invention relates generally to organic electroluminescent devices, and components thereof, which utilize organic small molecules or polymers that produce light when transferred into their excited state by an external power source. The excited state is created when positive and negative charges flow from opposite electrodes into the electroluminescent materials. Hole injection and/or hole transport materials forming a layer between one electrode and the electroluminescent material can improve the efficiency of the device (HIL or HTL layers). These devices and materials are of interest in, for example, monochrome and colored flat panel displays, organic-based light emitting diodes (OLEDS), signage, and white lighting.
It is of a great importance to improve the performance of currently existing devices including enhancing their efficiencies, longevity, tunability, as well as non-corrosiveness and better processability of the constituents. In particular, there is a demand for materials which can be easily processed from organic solvents and spin-cast onto electrodes to form very thin films having smooth, planar surfaces. Furthermore, lifetime stability, batch-to-batch reproducibility, resistivity control, and combinations of these properties are also of a great importance.
OLED materials and applications are generally described in Kraft et al., Angew. Chem. Int. Ed., 1998, 37, 402-428. One report showed unsatisfactory results in blending a conducting polymer system, PEDOT, with another polymer in HIL applications. See Elschner et al. (Bayer AG), Asia Display, IDW '01, pages 1427-1430. One reference describes problems with acidity in similar systems. See Gong et al., Applied Physics Letters, 83, no. 1, Jul. 7, 2003, pages 183-185. Polymer light emitting devices are called PLEDs.